Developer for alkaline-developable lithographic printing plates

ABSTRACT

An aqueous alkaline developing system for alkaline-developable lithographic printing plates and a method for its use are disclosed. The developing system comprises one or more water-soluble suppressors of the following structure:  
     R 1 (CHOH) n R 2    
     in which:  
     n is 4 to 7; and  
     either (i) R 1  is hydrogen, aryl, or CH 2 OH; and R 2  is alkyl group having 1 to 4 carbon atoms, CH 2 OR 3  in which R 3  is an alkyl group having 1 to 4 carbon atoms, CH 2 N(R 4 R 5 ) in which R 4  and R 5  are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, or CO 2 H; or (ii) R 1  and R 2  together form a carbon-carbon single bond. The developing system is especially suited for developing imageable elements useful as lithographic printing plates. The developing system is especially suited for use with elements in which (1) the imageable layer comprises at least one phenolic resin or at least one polymeric compound having pendent sulfonamide groups, and (2) the substrate is aluminum or and an aluminum alloy.

FIELD OF THE INVENTION

[0001] This invention relates to lithographic printing. In particular,this invention relates to a developing system for both positive-workingand negative-working imageable elements useful as alkaline-developablelithographic printing plates and to a method for its use.

BACKGROUND OF THE INVENTION

[0002] In lithographic printing, ink receptive regions, known as imageareas, are generated on a hydrophilic surface. When the surface ismoistened with water and ink is applied, the hydrophilic regions retainthe water and repel the ink, and the ink receptive regions accept theink and repel the water. The ink is transferred to the surface of amaterial upon which the image is to be reproduced. Typically, the ink isfirst transferred to an intermediate blanket, which in turn transfersthe ink to the surface of the material upon which the image is to bereproduced.

[0003] Imageable elements useful as lithographic printing plates,sometimes called printing plate precursors or printing forms, typicallycomprise an imageable layer applied over the surface of a hydrophilicsubstrate. The imageable layer includes one or more radiation-sensitivecomponents, which may be dispersed in a suitable binder. Alternatively,the radiation-sensitive component can also be the binder material.

[0004] To obtain a printing plate with imagewise distribution ofprintable regions, it is necessary to remove regions of an imagedimageable element. The most common method for removing the undesiredregions is to contact the imaged element with a developer. If afterexposure to radiation the exposed regions of the layer are removed bythe developer revealing the underlying hydrophilic surface of thesubstrate, the element is a positive-working printing element.Conversely, if the unexposed regions are removed, the element is anegative-working element. In each instance, the regions of the imageablelayer (i.e., the image areas) that remain after development areink-receptive, and the regions of the hydrophilic surface revealed bythe developing process accept water and aqueous solutions, typically afountain solution, and repel ink.

[0005] Many alkaline-developable positive-working imageable elementscomprise a light sensitive layer comprising a phenolic resin, such as anovolac resin, on a hydrophilic substrate, typically a specially treatedaluminum sheet. In one type of element, for example, the light sensitivelayer comprises a novolac resin and a radiation-sensitive o-diazoquinoneor diazonaphthoquinone compound, such as a naphthoquinonediazidesulfonic acid ester of a novolac resin. Upon exposure to light, theradiation-sensitive diazonaphthoquinone is converted to thecorresponding carboxylic acid. The developer penetrates and removes theexposed, or image regions of the imageable layer, revealing theunderlying hydrophilic surface of the substrate, without substantiallyaffecting the complimentary unexposed regions.

[0006] Certain negative-working printing plates contain novolac resins,a cross-linking agent, and a radiation-sensitive component that producesacid on exposure. Subsequent heating cures the exposed regions, so thatonly the unexposed areas can be removed by an alkaline developer. Theexposed regions, which remain after development, are oleophilic and willaccept ink.

[0007] In both types of printing plates, an alkaline developer canattack the imageable layer, front side (aluminum oxide) and/or thebackside (aluminum) of the imageable element. Developers for imageableelements that contain phenolic or similar resins typically comprisecomponents that suppress the attack of the high alkaline developereither on the substrate or on the imageable layer. Often there areproblems of miscibility of these components in the alkaline developer.Typically, silicate solutions (either as meta silicate or water glass)are used to protect aluminum substrates. In practice, this leads toproblems caused by silicate deposits on developed plates.

[0008] In addition, the activity of developers based on meta-silicatescannot be monitored by conductivity measurements. Therefore, a top-upmode is required leading to a high volume of wasted developer. In thismode, only the developer is used to keep the activity of the developerin the developing section of a processor constant. This requires about150 to 250 mL of developer per square meter of plate treated, from whichabout 100 to 200 mL are removed by an overflow device of the processor.

[0009] Therefore, a need exists for a developing system that protectsthe substrate from attack by an alkaline developer, that does not causeundesirable deposits on the developed printing plate, that requires onlya small number of components, and whose activity can be monitored byconductivity measurements.

SUMMARY OF THE INVENTION

[0010] The invention is a developing system for both positive-workingand negative-working imageable elements useful as lithographic printingplates. The developing system comprises both a developer and areplenisher.

[0011] The developer comprises an aqueous alkaline solution of one ofmore water-soluble suppressors of the following structure:

R₁(CHOH)_(n)R₂

[0012] in which n is 4 to 7; and

[0013] either (i) R₁ is hydrogen, aryl, or CH₂OH; and R₂ is alkyl grouphaving 1 to 4 carbon atoms, CH₂OR₃ in which R₃ is an alkyl group having1 to 4 carbon atoms, CH₂N(R₄R₅) in which R₄ and R₅ are eachindependently hydrogen or an alkyl group having 1 to 4 carbon atoms, orCO₂H; or (ii) R₁ and R₂ together form a carbon-carbon single bond. Thesesuppressors prevent attack by the alkaline developer on both the imageand on the aluminum substrate.

[0014] The aqueous alkaline solution has a pH of about 10.0, typicallygreater than about 11.0, to about 14.0; and the one or more suppressorstogether comprise about 10 wt % to about 30 wt % of the developer.

[0015] Although the developer may be used as its own replenisher,typically a specially formulated replenisher, which comprises all theingredients of the developer but which has a higher concentration ofbase is used as the replenisher.

[0016] preferred positive-working imageable element for use with thedeveloping system of the invention comprises an aluminum substrate andan imageable layer that comprises a phenolic resin, preferably a novolacresin. Preferred suppressors include N-methyl-glucamin, meso-inosit,gulonic acid gamma-lactone, and mixtures thereof.

[0017] In another aspect, the invention is a method for forming an imageusing the developing system. In another aspect, the invention is animage formed by the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION Developing System

[0018] Attack both on the imageable layer and on an aluminum or aluminumalloy substrate by a developer having a pH of greater than about 10 canbe suppressed by water-soluble organic compounds, or suppressors, havingthe following structure:

R¹(CHOH)_(n)R²

[0019] in which n is 4to 7; and

[0020] either (i) R¹ is H, aryl, or CH₂OH; and R² is alkyl group having1 to 4 carbon atoms, CH₂OR³ in which R³ is an alkyl group having 1 to 4carbon atoms, CH₂N(R⁴R⁵) in which R⁴ and R⁵ are each independently H oran alkyl group having 1 to 4 carbon atoms, or CO₂H; or (ii) R¹ and R²together form a carbon-carbon single bond.

[0021] Either a single suppressor or a mixture of suppressors may beused. The suppressor or the mixture of suppressors comprises about 10 wt% to about 30 wt % of the developer.

[0022] In one group of suppressors, R¹ and R² together form acarbon-carbon single bond. Included are carbocyclic compounds of thestructure: (CHOH)_(n), in which n is 4 to 7. In a preferred group ofsuppressors, n is 5 or 6, more preferably 6. There are nine possiblestereoisomers of 1,2,3,4,5,6-hexahydroxycyclohexane, several of whichare naturally occurring. A preferred suppressor is meso-inosit(cis-1,2,3,5-trans-4,6-hexahydroxycyclohexane). meso-Inosit can beisolated from corn steep liquor.

[0023] In another group of suppressors, R¹ is H, aryl, or CH₂OH; and R²is alkyl group having 1 to 4 carbon atoms, CH₂OR³ in which R³ is analkyl group having 1 to 4 carbon atoms, CH₂N(R⁴R⁵) in which R⁴ and R⁵are each independently H or an alkyl group having 1 to 4 carbon atoms,or CO₂H.

[0024] In one preferred group of suppressors, R¹ is H or CH₂OH; and R²is CO₂H. More preferably, R¹ is H and n is 4 or 5. This group includessuppressors of the structure H(CHOH)_(n)CO₂H, in which n is 4 or 5.Conceptually, these suppressors may be produced by oxidation of thealdehyde of the corresponding hexose or pentose sugar, i.e., oxidationof the aldehyde of a hexose sugar such as glucose, fructose, galactose,allose, mannose, etc, or oxidation of the aldehyde of a pentose sugarsuch as arabinose, ribose, xylose, etc. Gluconic acid [H(CHOH)₅CO₂H],for example, may be prepared by oxidation of glucose by, for example,microbiological oxidation. Preferred suppressors include ribonic acid,gluconic acid (dextronic acid), mannonic acid, and gulonic acid.

[0025] As is known to those skilled in the art, these suppressors mayexit in a ring-closed lactone form. Ribonic acid may exist as ribonicacid gamma-lactone. Gluconic acid may exist as gluconic acidgamma-lactone. Mannonic acid may exist as mannonic acid gamma-lactone.Gulonic acid may exist as gulonic acid gamma-lactone. The lactone formof these suppressors is included is the definition given above.

[0026] Also, as it apparent to those skilled in the art, in alkalinesolution the suppressor may exist as an anion [H(CHOH)_(n)CO₂ ⁻] due toionization of the carboxyl group (CO₂H) to the carboxylate anion (COO⁻).Lactose are converted to salts of the corresponding ring-opened acids inalkaline solution. Or the compound may be supplied as a salt, especiallyas an alkali metal salt, such as a sodium salt [H(CHOH)_(n)CO₂ ⁻Na⁺], ora potassium salt [H(CHOH)_(n)CO₂ ⁻K⁺]. Anions and salts of thesesuppressors are included in the definition given above.

[0027] In another group of suppressors, R¹ is hydrogen, and R² isCH₂N(R⁴R⁵) in which R⁴ and R⁵ are each independently hydrogen or analkyl group having 1 to 4 carbon atoms. n is preferably 4 or 5, and R⁴and R⁵ are preferably each independently hydrogen or an alkyl grouphaving 1 to 2 carbon atoms. Preferred suppressors include glucamine,N-methyl-glucamine, and 1-desoxy-1-(methylamino)-galactit. A morepreferred suppressor is N-methyl-glucamine.

[0028] The developer has a pH between about 10 and about 14.0, typicallyat least about 11, preferably at least about 12, and preferably lessthan about 13.5. The alkalinity of the developer can be achieved by anyof the conventional alkaline systems; e.g. alkali metal hydroxides,silicates, phosphates, borates, amines etc. Alkali metal hydroxides arepreferred. Silicates are not favored because silicate deposits can beformed on the exposed and developed image. Consequently, the developerpreferably does not comprise a silicate.

[0029] The developer may additionally comprise materials that areconventional components of developers, such as, surfactants (weftingagents), biocides (antimicrobial and/or antifungal agents), antifoamingagents, such as certain silicones, buffers, chelating (complexing)agents, etc, in a suitable amount (for example up to 5 wt % based on thetotal composition weight). If the developer is used in combination withand/or diluted with hard water, the presence of a chelating agent ispreferred. Salts of ethylenediamine tetraacetic acid, for example, canbe used as both a buffer and a chelating agent.

[0030] The developer may be a wholly aqueous developer, i.e., one thatdo not comprise an organic solvent, or it may comprise a small amount ofone or more organic solvents, such as are disclosed in Fiebag, U.S. Pat.No. 6,143,479, incorporated herein by reference. Polyglycol derivativeswith the structure:

R⁶O—(CH₂CHR⁷O)_(y)—R⁸

[0031] in which R⁶ is hydrogen or C₁-C₈ alkyl; R⁷ is hydrogen, methyl orethyl; R⁸ is hydrogen or CH₂COOH; and y is an integer from 10 to 20, maybe included. Polycondensation products of C₂-C₄ alkylene oxides withethylene diamine may also be included. Mixture of polyglycol derivativesmay also be used. Preferred polyglycol derivatives are polypropyleneglycol ether, polyethylene glycol ether, polybutylene glycol ether,derivatives thereof, and mixtures thereof.

[0032] Glycols with the structure:

R⁹—CH(OH)—(CH₂)_(z)—CH(OH)—R¹⁰

[0033] in which z is 0, 1, or 2; and R⁹ and R¹⁰ are each independentlyhydrogen or C₁-C₃ alkyl, may be included. Preferred glycols are ethyleneglycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and mixturesthereof.

[0034] When present, the total amount of polyglycol derivative orderivatives present typically comprises about 0.0005 wt % to about 3 wt% of the developer, based on the total weight of the developer. Whenpresent, the total amount of glycol pr glycols present typicallycomprises about 3 wt % to about 8 wt % of the developer, based on thetotal weight of the developer.

[0035] The developer may be conveniently prepared by dissolving thecomponents in water. It can be supplied in a form ready for use, or itcan also be provided in the form of a concentrate, which is diluted withwater by the user prior to use.

[0036] Although the developer can also be used as its own replenisher,preferably, a specially formulated replenisher is used. In thereplenisher, the concentration of base is higher than the concentrationof base in the developer to compensate for the base consumed in thedevelopment process. Thus, a balance between developer drag-out anddeveloper feed-in is reached. There is a correlation between the valueof the electric conductivity and the alkalinity of the total developerbath.

[0037] The replenisher comprises the same components as the developer.The only difference is that the electrical conductivity of thereplenisher has to be higher than that of the corresponding developer(i.e., the conductivity of the developer is lower than that of thecorresponding replenisher). This is can, for instance, be obtained byhaving a higher concentration of the alkali metal hydroxide in thereplenisher. The replenisher typically has a pH of about 11.0 to about14.

[0038] As soon as a reduction of developer efficiency is detected by alower electrical conductivity in the developing bath, replenisher isadded to the developer until the electrical conductivity of thedeveloper reaches its original value. The developer preferably has aconductivity of about 40 to about 80 mS/cm at 20° C. The conductivity ofthe replenisher is higher than that of the developer, typically fromabout 60 to about 120 mS/cm at 20° C.

Imageable Elements

[0039] The imageable element comprises an imageable layer on ahydrophilic substrate.

Substrate

[0040] The hydrophilic substrate, i.e., the substrate that comprises atleast one hydrophilic surface, comprises a support, which may be anymaterial conventionally used to prepare imageable elements useful aslithographic printing plates. The support is preferably strong, stableand flexible. It should resist dimensional change under conditions ofuse so that color records will register in a full-color image.Typically, it can be any self-supporting material, including, forexample, polymeric films such as polyethylene terephthalate film,ceramics, metals, or stiff papers, or a lamination of any of thesematerials. Metal supports include aluminum, zinc, titanium, and alloysthereof.

[0041] Although the developers may be used with imageable elements thatcomprise any type of substrate known in the art, they are particularlywell adapted for use with those that comprise an aluminum or an aluminumalloy support. The surface of the aluminum support may be treated bytechniques known in the art, including physical graining,electrochemical graining, chemical graining, and anodizing. Thesubstrate should be of sufficient thickness to sustain the wear fromprinting and be thin enough to wrap around a printing form, typicallyfrom about 100 to about 600 μm.

[0042] Typically, the substrate comprises an interayer between thealuminum support and the imageable layer. The interlayer may be formedby treatment of the support with, for example, silicate, dextrine,hexafluorosilicic acid, phosphate/fluoride, polyvinyl phosphonic acid(PVPA) or polyvinyl phosphonic acid copolymers.

Imageable Layer

[0043] The imageable layer comprises either a positive-working or anegative-working imageable composition. The composition may be sensitiveto ultraviolet and/or visible radiation (i.e., photoimageable), and/orit may be thermally imageable.

[0044] Positive-working photoimageable compositions are well known. Theyare discussed, for example, in Chapter 5 of Photoreactive Polymers: theScience and Technology of Resists, A. Reiser, Wiley, New York, 1989, pp.178-225. These compositions comprise a water insoluble, alkali solublebinder and a material that comprises a photosensitive moiety. Thephotosensitive moiety may be bonded to the binder and/or be present in aseparate compound.

[0045] The binder may comprise a phenolic resin, such as a novolacresin. Novolac resins are commercially available and are well known.They are typically prepared by the condensation reaction of a phenol,such as phenol, m-cresol, o-cresol, p-cresol, etc, with an aldehyde,such as formaldehyde, paraformaldehyde, acetaldehyde, etc. or ketone,such as acetone, in the presence of an acid catalyst. The weight averagemolecular weight is typically about 1,000 to 15,000. Typical novolacresins include, for example, phenol-formaldehyde resins,cresol-formaldehyde resins, phenol-cresol-formaldehyde resins,p-t-butylphenol-formaldehyde resins, and pyrogallol-acetone resins.Particularly useful novolac resins are prepared by reacting m-cresol,mixtures of m-cresol and p-cresol, or phenol with formaldehyde usingconventional conditions.

[0046] Other phenolic resins include polyvinyl compounds having phenolichydroxyl groups. Such compounds include, for example, resole resins,polymers of hydroxystyrene (vinyl phenol), such aspoly(p-hydroxystyrene); copolymers containing recurring units ofhydroxystyrene; and polymers and copolymers containing recurring unitsof substituted hydroxystyrenes, such as acrylate and methacrylatecopolymers of hydroxystyrene.

[0047] The binder may also be a water insoluble, base soluble polymericcompound having pendent sulfonamide groups, such as is described inAoshima, U.S. Pat. No. 5,141,838 (EP 330,239). Particularly usefulpolymeric materials comprise (1) a sulfonamide monomer unit, especiallyN-(p-aminosulfonylphenyl)methacrylamide,N-(m-aminosulfonylphenyl)methacrylamideN-(o-aminosulfonylphenyl)methacrylamide, and/or the correspondingacrylamide, more especially N-(p-aminosulfonylphenyl)methacrylamide; (2)acrylonitrile and/or methacrylonitrile; and (3) methyl methacrylateand/or methyl acrylate.

[0048] The photosensitive moiety is typically the o-diazonaphthoquinonemoiety. Compounds that contain the o-diazonaphthoquinone moiety (i.e.,quinonediazides), preferably compounds that comprise ano-diazonaphthoquinone moiety attached to a ballasting moiety that has amolecular weight of at least 1500, but less than about 5000, arepreferred. Typically, these compounds are prepared by the reaction of a1,2-naphthoquinone diazide having a halogenosulfonyl group, typically asulfonylchloride group, at the 4- or 5-position with a mono- orpoly-hydroxyphenyl compound, such as mono- or poly-hydroxy benzophenone.

[0049] The phenolic resin may be derivatized with ano-diazonaphthoquinone moiety. Polymeric diazonaphthoquinone compoundsinclude derivatized resins formed by the reaction of a reactivederivative that contains diazonaphthoquinone moiety and a polymericmaterial that contains a suitable reactive group, such as a hydroxyl oramino group. Suitable polymeric materials for forming these derivatizedresins include the novolac resins, resole resins, polyvinyl phenols,acrylate and methacrylate copolymers of hydroxy-containing monomers suchas hydroxystyrene. Representative reactive derivatives include sulfonicand carboxylic acid, ester, or amide derivatives of thediazonaphthoquinone moiety. Derivatization of phenolic resins withcompounds that contain the diazonaphthoquinone moiety is well known inthe art and is described, for example, in West, U.S. Pat. Nos.5,705,308, and 5,705,322.

[0050] A mixture comprising one or more phenolic resins and/or one ormore polymeric compounds having pendent sulfonamide groups may also beused as the binder in the positive-working photosensitive compositions.

[0051] Positive-working thermally imageable layers comprise a binder, adissolution suppressor, and optionally, a photothermal conversionmaterial. Such systems are disclosed in, for example, Parsons, WO97/39894; Nagasaka, EP 0 823 327; Miyake, EP 0 909 627; West, WO98/42507; and Nguyen, WO 99/11458, all of which are incorporated hereinby reference. The binder is typically a phenolic resin, such as anovolac resin, as discussed above. The dissolution suppressors arebelieved not to be sensitive, i.e. photoreactive, themselves toradiation in the range of about 600 nm to about 800 nm and radiation inthe range of about 800 nm to about 1200 nm, the radiation typically usedto image a thermally imageable element.

[0052] The dissolution suppressor may be a compound that comprises ano-diazo-naphthoquinone moiety, such as is discussed above. Thederivatized resins that comprise an o-diazonaphthoquinone moiety can actas both the binder and the dissolution suppressor. They can be usedalone, or they can be combined with other binders and/or dissolutionsuppressors. Other compounds useful as dissolution suppressors include,compounds that contain a positively charged (i.e., quaternized) nitrogenatom, for example, tetraalkyl ammonium compounds, quinolinium compounds,benzothiazolium compounds, pyridinium compounds, and imidazoliumcompounds. A preferred group of dissolution suppressor compoundsincludes those that are also dyes, especially triarylmethane dyes suchas ethyl violet. These compounds can also act as contrast or colorationdyes, which distinguishes the unimaged regions from the imaged regionsin the developed imageable element.

[0053] Alternatively, or additionally, the binder itself can comprisepolar groups that act as acceptor sites for hydrogen bonding with thehydroxy groups present in the polymeric material and, thus, act as adissolution suppressor. Using well-known methods, a portion of thehydroxyl groups of the binder can be derivatized to introduce polargroups, for example carboxylic acid esters, such as benzoate esters;phosphate esters; ethers, such as phenyl ethers; and sulfonic acidesters, such as methyl sulfonates, phenyl sulfonates, p-toluenesulfonates (tosylates), and p-bromophenyl sulfonates (brosylates).

[0054] Derivatization of the hydroxyl groups of the binder increases itsmolecular weight and reduces the number of hydroxyl groups, typicallyreducing both its solubility and rate of dissolution in the developer.Although it is important that the level of derivatization be high enoughthat the binder also acts as a dissolution suppressor, it should not beso high that, following thermal imaging the binder is not soluble in thedeveloper. Although the degree of derivatization required will depend onthe nature of the binder and the nature of the moiety containing thepolar groups introduced into the binder, typically about 0.5 mol % toabout 5 mol %, preferably about 1 mol % to about 3 mol %, of thehydroxyl groups will be derivatized. These derivatized binders can beused either alone or in combination with other polymeric materialsand/or dissolution suppressors.

[0055] One preferred group of binders that comprise polar groups andfunction as dissolution suppressors are derivatized phenolic polymericmaterials in which a portion of the phenolic hydroxyl groups have beenconverted to sulfonic acid esters, preferably phenyl sulfonates orp-toluene sulfonates. Derivatization can be carried by reaction of thepolymeric material with, for example a sulfonyl chloride such asp-toluene sulfonyl chloride, in the presence of a base such as atertiary amine. A preferred derivatized binder is a derivatized novolacresin in which about 1 mol % to 3 mol %, preferably about 1.5 mol % toabout 2.5 mol %, of the hydroxyl groups have been converted to phenylsulfonate or p-toluene sulfonate (tosyl) groups.

[0056] When a photothermal conversion material is present, it maycomprise infrared absorber or dye bound to a phenolic material (i.e., aphenolic material derivatized with an infrared absorber or infraredabsorbing dye). If an appropriate infrared absorber or dye is selected,the derivatized polymeric material can act as the binder, thedissolution suppressor, and/or the photothermal conversion material.

[0057] The imageable layer may also comprise dye to aid in the visualinspection of the exposed and/or developed element. Printout dyes areadded to distinguish the exposed regions from the unexposed regionsbefore and during processing. Contrast or coloration dyes are added todistinguish the unimaged regions from the imaged regions in thedeveloped element.

[0058] If the imageable element is to be imaged with infrared or nearinfrared radiation, the imageable layer absorbs the imaging radiation,preferably radiation in the range of about 800 nm to 1200 nm, theradiation is commonly used for imaging thermally imageable elements. Anabsorber called a photothermal conversion material, which absorbradiation and convert it to heat, is typically present in the imageablelayer. Photothermal conversion materials may absorb ultraviolet,visible, and/or infrared radiation and convert it to heat. Although thebinder may itself comprise an absorbing moiety, i.e., be a photothermalconversion material, typically the photothermal conversion material is aseparate compound.

[0059] The photothermal conversion material may be either a dye orpigment, such as a dye or pigment of the squarylium, cyanine,merocyanine, indolizine, pyrylium, or metal diothiolene class. Examplesof absorbing pigments are Projet 900, Projet 860, and Projet 830 (allavailable from the Zeneca Corp.). Carbon black pigments may also beused. Because of their wide absorption bands, carbon black-based platescan be used with multiple infrared imaging devices having a wide rangeof peak emission wavelengths.

[0060] Dyes, especially dyes that are soluble in the aqueous alkalinedeveloper, are preferred to prevent sludging of the developer byinsoluble material. The dye may be, for example, an indoaniline dye,oxonol dye, porphyrin derivatives, anthraquinone dye, merostyryl dye,pyrylium compound, or a squarylium derivative. Absorbing dyes aredisclosed in numerous disclosures and patent applications in the field,for example, Nagasaka, EP 0,823,327; Van Damme, EP 0,908,397; DeBoer,U.S. Pat. No. 4,973,572; Jandrue, U.S. Pat. No. 5,244,771; and Chapman,U.S. Pat. No. 5,401,618.

[0061] The amount of photothermal conversion material in the imageablelayer is generally sufficient to provide an optical density of at least0.05, and preferably, an optical density of from about 0.5 to about 2 atthe imaging wavelength.

[0062] In another embodiment of this invention, a negative-working,alkaline developable printing plate, typically one containing a novolacresin and/or another phenolic resin, is imagewise exposed with asuitable light source and heated to harden the exposed regions. Thesematerials are described, for example, in Haley, U.S. Pat. No. 5,372,907;Haley U.S. Pat. No. 5,466,557; and Nguyen, U.S. Pat. No. 5,919,601.

[0063] Haley '907 discloses a radiation-sensitive composition that issensitive to both ultraviolet and infrared radiation. The compositioncomprises (1) a resole resin, (2) a novolac resin, (3) a latent Bronstedacid and (4) an infrared absorber. The solubility of the composition inan alkaline developer is both reduced in exposed areas and increased inunexposed areas by the steps of imagewise exposure to activatingradiation and heating.

[0064] Latent Brönsted acids are precursors that form a Brönsted acid bythermally or photochemically initiated decomposition. The Bronsted acidis believed to catalyze a matrix-forming reaction between the resoleresin and the novolac resin. Latent Brönsted acids include, for example,onium salts in which the onium cation is iodonium, sulphonium,phosphonium, oxysulphoxonium, oxysulphonium, sulphoxonium, ammonium,diazonium, selononium, or arsonium, and the anion is a non-nucleophilicanion selected from tetra-fluoroborate, hexafluorophosphate,hexafluoroarsenate, hexafluoroantimonate, triflate,tetrakis(pentafluoro-phenyl)borate, pentafluoroethyl sulfonate,p-methyl-benzyl sulfonate, ethyl sulfonate, trifluoromethyl acetate, andpentafluoroethyl acetate. Typical latent Brönsted acids include, forexample, diphenyliodonium hexafluorophosphate, diphenyl iodoniumhexafluoroantimonate, bis-4-dodecylphenyliodonium hexafluoro antimonate,dicumyliodonium hexofluorophosphate, and triphenylsulfoniumhexafluoroantimonate. Non-ionic latent Brönsted acids include, forexample, haloalkyl-substituted s-triazines, which are described, forexample, in Smith, U.S. Pat. No. 3,779,778.

[0065] Nguyen discloses radiation-sensitive compositions imageable byinfrared and ultraviolet/visible radiation. These compositions comprisea thermal-activated acid generator; a crosslinking resin; a binder resincomprising a polymer containing reactive pendant groups selected fromhydroxy, carboxylic acid, sulfonamide, and alkoxymethylamides; aninfrared absorber; and optionally an ultraviolet/visibleradiation-activated acid generator for ultraviolet/visiblesensitization. The thermal-activated acid generators are typically thesame as the latent Brönsted acids described above.

[0066] Conventional additives, such as dyes, pigments, plasticizers,sensitizers, stabilizers, surfactants, and components, such asleucodyes, that produce print-out images can be included in thesenegative-working, alkaline developable compositions.

Imaging and Processing

[0067] Imaging may be carried out by well-known methods. When theelement is “positive working,” the exposed regions are removed to revealthe underlying hydrophilic surface of the substrate. When the element is“negative working,” the unexposed regions are removed to reveal theunderlying hydrophilic surface of the substrate.

[0068] If the element is a photoimageable element, it may be exposed toactinic radiation from a source of light that is absorbed by thephotoreactive component or components present. Conventional exposuresources include, for example, carbon arc lamps, mercury lamps, xenonlamps, tungsten lamps, metal halide lamps, and lasers emitting at theappropriate wavelength. Diazonaphthoquinone compounds substituted in the5-position typically absorb at 345 nm and 400 nm. Diazonaphthoquinonecompounds substituted in the 4-position typically absorb at 310 nm and380 nm. Imagewise exposure is typically carried out through a photomask,but direct digital exposure with a laser emitting at the appropriatewavelength is also possible.

[0069] If the element is a thermally imageable element, it may be imagedwith a laser or an array of lasers emitting modulated near infrared orinfrared radiation in a wavelength region that is absorbed by theelement. Infrared radiation, especially infrared radiation in the rangeof about 800 nm to about 1200 nm, is typically used for imaging athermally imageable element. Imaging is conveniently carried out with alaser emitting at about 830 nm or at about 1056 nm. Suitablecommercially available imaging devices include image setters such as aCreo Trendsetter (CREO, British Columbia, Canada) and a Gerber Crescent42T (Gerber).

[0070] Alternatively, the thermally imageable element may be imagedusing a conventional apparatus containing a thermal printing head. Animaging apparatus suitable for use in conjunction with the imageableelements includes at least one thermal head but would usually include athermal head array, such as a TDK Model No. LV5416 used in thermal faxmachines and sublimation printers. When exposure is carried out with athermal head, it is unnecessary that the element absorb infraredradiation. However, elements that absorb infrared radiation can beimaged with a thermal head.

[0071] Imaging produces an imaged element, which comprise a latent imageof imaged and unimaged regions. Developing the imaged element to form adeveloped element converts the latent image to an image by removing theexposed, or imaged, regions and revealing the hydrophilic surface of theunderlying substrate.

[0072] Typically, the developer is applied to the imaged element byrubbing or wiping the imageable layer with an applicator containing thedeveloper. Alternatively, the imaged element may be brushed with thedeveloper or the developer may be applied to the element by spraying theimageable layer with sufficient force to remove the exposed regions. Ineither instance, a developed element is produced. Development may becarried out in a commercially available processor, such as a MercuryProcessor (Kodak Polychrome Graphics). The Mercury Processor is equippedwith an immersion type developing bath, a section for rinsing withwater, a gumming section, and a drying section. Additional, aconductivity-measuring unit can be incorporated into the processor.

[0073] Development of both positive-working and negative-working imagedelements is typically carried out at a temperature of from about 18° C.to about 28° C., for a period of from about 5 seconds to about 60seconds.

[0074] After a certain number of imaged elements have been developed,the conductivity value falls below a predetermined level. Then thereplenisher is added to the processor section that contains thedeveloper. Usually about 30 mL to about 100 mL, typically about 50-80mL, of replenisher per 1 m² of imaged element processed is necessary tokeep both the volume of developer and its conductivity value constant.

[0075] The developed element, typically a lithographic printing memberor a printing plate, comprises regions in which imageable layer has beenremoved revealing the underlying surface of the hydrophilic substrate,and complimentary regions in which the imageable has not been removed.The regions in which the imageable layer has not been removed are inkreceptive and correspond to the regions that were not exposed duringimaging.

[0076] Following development, the developed element is rinsed with waterand dried. Drying may be conveniently carried out by infrared radiators.

[0077] After drying, the developed element is treated with a gummingsolution. A gumming solution comprises one or more water solublepolymers, for example polyvinylalcohol, poly(meth)acrylic acid,poly(meth)acrylamide, polyhydroxyethyl(meth)acrylate,polyvinylmethylether, gelatin, and polysaccharide such as dextran,pullulan, cellulose, gum arabic, and alginic acid. A preferred materialis gum arabic.

[0078] A developed and gummed plate can also be baked to increase therun length of the plate. Baking can be carried out, for example at about220° C. to about 240° C. for about 7 to 10 minutes, or at a temperatureof 120° C. for 30 min.

INDUSTRIAL APPLICABILITY

[0079] The developing system is especially suitable for developingimageable elements useful as positive-working lithographic printingplates. It is especially suited for use with elements in which (1) theimageable layer comprises at least one phenolic resin that is insolublein water and removable by the aqueous alkaline developer and/or at leastone polymeric compound having pendent sulfonamide groups that isinsoluble in water and removable by the aqueous the aqueous alkalinedeveloper, and (2) the substrate is aluminum or and an aluminum alloy.

[0080] In practice not every developer works well with every printingplate, especially with those that have different interlayers. The attackof a developer on the aluminum substrate depends on the composition ofthe developer. Therefore, printers who use printing plates withdifferent interlayers must store and use a developer for each type ofplate. Because the developer of the invention suppresses attack onaluminum substrates, it can be used with printing plates having avariety of interlayers. Because the developer does not contain asilicate solution (either as metasilicate or an alkali metal waterglass), silicate deposits on developed plates are eliminated. Becausethe conductivity of the developer can be monitored, the inventionprovides a developing system that makes it relatively easy for anoperator to work with a constant activity developer.

[0081] The advantageous properties of this invention can be observed byreference to the following examples, which illustrate but do not limitthe invention. In the specification, examples, and claims, unlessindicated otherwise, all percentages are percentages by weight based onthe weight of the developer.

EXAMPLES

[0082] Glossary REWOTERIC ® AM-V Sodium capryloamphoacetate wettingagent (Witco, Perth Amboy, NJ, USA) SYNPERONIC ® T 304 Poloxamine 304;Polyoxyethylene, polyoxypropylene liquid block copolymer of ethylenediamine (I.C.I. Am., Wilmington, DE, USA) TRILON ® B chelating Tetrasodium ethylenediamine tetraacetic acid agent (BASF, Ludwigshafen,Germany)

[0083] N-Methyl-D-glucamin, meso-inosit(cis-1,2,3,5-trans-4,6-hexahydroxycyclohexane), and L-gulonic acidgamma-lactone were obtained from Aldrich, Milwaukee, Wis., USA.

Preparation of Developers and Replenishers

[0084] The following developers and repelenishers were prepared bystirring the components together:

[0085] Developer 1—839 g water, 140 g N-methyl-D-glucamin, and 21 gsodium hydroxide.

[0086] Developer 2—839 g water, 140 g meso-inosit, and 21 g sodiumhydroxide.

[0087] Developer 3—84.6 kg water, 14.0 kg meso-inosit, 2.1 kg sodiumhydroxide, and 0.24 kg SYNPERONIC® 304 T.

[0088] Developer 4—708.5 g water, 140 g L-gulonic acid gamma-lactone,120 g sodium meta-silicate penta-hydrate, and 31.5 g sodium hydroxide.

[0089] Developer 5—81.7 g water, 15 g meso-inosit, 2.9 g potassiumhydroxide. 0.2 g TRILON® B chelating agent B, and 0.2 g REWOTERIC® AM-Vwetting agent.

[0090] Replenisher 1—83.3 kg water, 14.0 kg meso-inosit, 3.4 kg sodiumhydroxide, and 0.24 kg SYNPERONIC® 304 T.

Preparation of Comparative Developers

[0091] Comparative developers 1-4 were prepared by mixing the componentsgiven in Table1. TABLE 1 Compar. Compar. Compar. Compar. ComponentExample 1 Example 2 Example 3 Example 4 Water 979 g 880 g 976.6 g 877.6g Sodium hydroxide 21 g 21 g Sodium meta-silicate 5- 120 g 120 g hydrateSYNPERONIC ® 304-T 2.4 g 2.4 g

Substrate Attack Test

[0092] The weight loss for 1 dm² aluminum discs having differentinterlayers but no imageable layer was determined by treating the discswith developer containing different wt % of suppressor. Weight loss wasmeasured by comparing the initial weight of the disc with the weight ofthe disc after it laid in the developer composition for 5 min at 20° C.Comparative Developers 1 and 2 containing differing amounts of inventivesuppressors were evaluated. A developer containing SYNPERONIC® 304-T(Comparative Examples 3 and 4), which is a suppressor for the imageablelayer only, was also evaluated. The results are shown in Tables 2 and 3below. TABLE 2 Weight loss (in mg) of a 1 dm² aluminum disc in 2.1 wt %sodium hydroxide Polyvinyl Phosphate/- Phosphonic Fluoride Silicate Acid(PVPA) Wt % Untreated Treated Treated Treated suppressor^(a) substrateSubstrate Substrate Substrate None^(b) 5.3 7.3 0.9 10.3 3.75 5.2 4.9 7.47.1 0.3 0.2 10.3 10.2  7.5 3.5 3.4 6.5 6.3 0.1 0.0  7.5 7.4 11.25 2.12.2 4.9 5.0 0.0 0.0  5.8 5.7 15 1.2 1.3 4.2 4.0 0.0 0.0  5.0 5.0Comparative 5.4 7.2 1.0 10.3 Developer 3

[0093] TABLE 3 Weight loss (in mg) of a 1 dm² aluminum disc in 12 wt %sodium meta-silicate pentahydrate Untreated Phosphate/ Wt %supressor^(a) substrate Fluoride Silicate PVPA None^(b) 0.9 2.1 0.1 2.03.75 0.8 0.7 1.9 1.8 0.1 0.0 1.9 1.8 7.5 0.7 0.7 1.6 1.6 0.0 0.1 1.3 1.211.25 0.4 0.4 1.3 1.2 0.1 0.0 0.9 1.0 15 0.3 0.3 0.8 0.7 0.0 0.0 0.6 0.5Comparative 0.9 2.0 0.1 2.0 Developer 4^(c)

[0094] For all substrates there was little or no attack on the aluminumdisc when an appropriate concentrations of suppressor was present in thedeveloper. When only SYNPERONIC® 304-T was present, there was attack onall substrates.

Exposure and Developing of the Positive-working Printing Plates

[0095] EASYPRINT® and Virage™ positive-working lithographic printingplates (Kodak Polychrome Graphics LLC) were cut into 790 mm×850 mm testsamples and exposed with a metal halide lamp (MH-Burner, available fromSack) with 510 mJ/cm² (EASYPRINT®) and 525 mJ/cm² (Virage™) under asilver halide film half-step wedge (Fogra) with a density range of 0.15to 1.95 increments as a positive copy.

[0096] A commercially available processor (Mercury 850; Kodak PolychromeGraphics LLC), equipped with an immersion type developing bath, asection for rinsing with water, a gumming section, and a drying section,was used to develop the exposed plates. The processor was filled with 60L of the appropriate developer. If the processor contains more than thegiven 60 L, the excess is removed via an overflow. This excess can becollected in a container. Separately, a container for the replenisherwas attached from which a predetermined amount of replenisher per squaremeter of exposed plate was added to the developing bath via a pump.

[0097] The activity of the developer was examined with the help of itsconductivity and by titration of the amount of alkali. The conductivityof the developing bath was monitored by an incorporated SIPAN 3conductivity measuring unit (Siemens). To determine the alkali content,10 mL of the developer was removed from the developing bath, 90 mLdeionized water was added, and the titration was carried out with 0.5 NHCl (Titrino DMS 716, Metrohm). The number of mL used to reach the firstequivalence point is referred to as alkali value.

[0098] The temperature of the developing bath, (23±1)° C., and dwelltime in the developer, 25 sec, were kept constant in all tests.

[0099] To evaluate the copies obtained after development, the followingcriteria were examined. (1) Number of steps after gray wedge exposurethat do not retain coating after development (in the following referredto as GW—the lower the number the less image attack); (2) Microlines ina test pattern to assess resolution that have not been attacked (in thefollowing referred to as ML—the lower the number the greater theresolution indicating less image attack); and (3) Behavior during theprint proof or during restarting of the printing (ink acceptanceproblems of the image and non-image areas—i.e. “toning”).

[0100] To obtain the latter test results, the exposed and developedplates were mounted in a sheet-fed offset press and proofed. The imageareas accepted ink without any problems and the paper copies did notshow any background (referred to as toning) in the non-image areas.After about 2000 copies, the press was stopped for about 45 minutes andthen restarted (restarting test). The same results as at the beginningof the printing test were obtained. In particular the non-image areasdid not show any toning, which indicates a good protection of the basismaterial by the developer.

Copying Results

[0101] The copying results with EASYPRINT® and Virage™ plates and thedevelopers of the invention are listed in Table 4 below. TABLE 4 CopyingResults Compar. Compar. Parameter Exam. 1 Exam. 2 Exam. 3 Exam. 4 Exam.5 Exam. 1 Exam. 2 EASYPRINT ® GW  3  3  3 3/4  3 5/6  6 ML 10/12 10/1212 12/15 12 20/25 20/25 Print no toning no toning no toning no toning notoning toning toning Virage ™ GW 3 3/4 3 3/4 3/4  6 6 ML 12  12 10/12 1212 25 20/25 Print no toning no toning no toning no toning no toningtoning toning

Stability and Load Tests of EASYPRINT® Plates

[0102] EASYPRINT® plates exposed with the Fogra wedge in the same manneras described above were developed one after another at a rate of 140plates per day for 25 days (plus 4 weekend interruptions) in the Mercury850 processor. The quality of the resulting copies was evaluated interms of the GW and the ML values. The activity of the developer wasmonitored at a throughput of 4 m²/L by conductivity measurements and bytitration with 0.5 N HCl.

[0103] The results for developer 3 and the corresponding replenisher 1are listed in Table 5. Titration and conductivity data show that theactivity of the developer can be kept constant during long testingperiod by the addition of 80 mL/m² of developed plate. This is apparentin the almost constant values for the copy parameters gray scale 2 wedgeand microlines after the development of 3500 m plates in the 60 L ofdeveloper in the processor. Throughout the course of the test, 175 L ofoverflow of used developer was collected which corresponds to a value of50 mL/² of developed plate.

[0104] During the test period, the developing process was not affectedby either the formation of foam or the precipitation of insolublematerial on the bottom of the processor. After testing was completed,the processor could be easily cleaned by rinsing with water, and noresidue remained.

[0105] After a throughput of 20, 40 and 58.3 m²/L, EASYPRINT® plates didnot show any irregularities in the printing test. Neither ink acceptancenor toning problems occurred. TABLE 5 Data of stability and load testTitration Throughput Gray Replenisher mL 0.5 N Conductivity (m²/L)Microlines scales (mL/m²) HCl) (mS/cm) 0 12 3 10.8 58.4 4 12 3 80 10.658.2 8 12/15 3 to 4 80 10.8 58.3 12 12 3 80 10.4 57.9 16 12 3 to 4 8010.5 58.1 20 12/15 3 80 10.3 57.8 24 12 3 80 10.6 58.0 28 12 3 80 10.458.1 32 12/15 3 to 4 80 10.3 57.9 36 12 3 80 10.7 57.8 40 12/15 3 to 480 10.5 58.0 44 12 3 80 10.4 57.7 48 12/15 3 80 10.5 57.9 52 12/15 3 to4 80 10.5 57.8 58.3 12/15 3 to 4 10.4 58.0

Developing of Positive-Working Thermal Plate

[0106] ELECTRA® positive-working thermal printing plates (KodakPolychrome Graphics LLC) were cut into 515 mm×790 mm test samples. Thetest samples were exposed in a Trendsetter 3244 (Creo) infrared exposureunit at an energy of 10 W and a rotational speed of the drum of 180 rpm.The Kodak Professional COLORFLOW® Strip (Eastman Kodak), which containsdifferent elements for evaluating the quality of the copies, was usedfor evaluation.

[0107] A commercially available processor (Sprinter; Kodak PolychromeGraphics LLC), equipped with an immersion type developing bath, asection for rinsing with water, and a gumming and drying section, wasused to develop the imagewise exposed plates. The processor was filledwith 20 L of the appropriate developer. Separately, a container for thereplenisher was attached from which a predetermined amount ofreplenisher per square meter of exposed plate was added to thedeveloping bath via a pump.

[0108] The temperature of the developing bath, (23±1)° C., and the dwelltime in the developer, 45 sec, were kept constant in all tests.

[0109] The activity of the developer was examined with the help of itsconductivity and by titration of the amount of alkali. The conductivityof the developing bath was monitored by a separately mountedconductivity measuring unit (Conductivity Monitor, Unigraph). Toevaluate the copies obtained after development, the following criteriawere examined: reproduction of the 1 and 2 pixel elements, opticaldensity (OD) of the checkerboard dots of the pixel elements (measuredwith the apparatus D 19C/D196 from Gretag/Macbeth).

[0110] The tests using developers 3 and 4 provided the followingresults:

[0111] (1) The image areas were not attacked which follows fromunchanged optical density of the image areas as compared with thenon-treated areas.

[0112] (2) The 1 and 2 pixel elements were well reproduced.

[0113] (3) The optical density for 50% dot was measured to be OD=50 withdeveloper 3 and OD=49 for developer 4.

[0114] For the stability and load test exposed ELECTRA® plates weredeveloped in the manner described above one after another at a rate of33 plates per day for 30 days (plus 5 weekend interruptions) in theSprinter processor filled with developer 3. For replenishment thereplenisher 1 was used. To determine the alkali content, 10 mL of thedeveloper was removed from the developing bath, 90 mL deionized waterwas added, and titration was carried out with 0.5 N HCl (Titrino DMS716, Metrohm). The number of mL used to reach the first equivalencepoint is referred to as alkali value. The quality of the resultingcopies was evaluated in terms as above. At a throughput of 2 m²/L theelectrical conductivity was measured as well as the developer activity.

[0115] Addition of 82 mL of replenisher kept the activity of thedeveloper constant until the end of testing of 15 m²/L (electricalconductivity: 58.4 mS/cm; titration: 10.8 mL). The copy parameters of OD(optical density)=94 for 95% dot screen and OD=50 for 50% dot screen inthe beginning only slightly changed to OD=95 and OD=51, respectively, atthe end of the test. The reproduction of the 1 and 2 pixel elements didnot change.

[0116] Plates developed with this developing system showed no problemsin ink acceptance or toning during the printing test at the print proofand upon restart.

[0117] When positive-working thermal printing plate exposed as abovewere developed with the Comparative Developers 1 to 4, both the 1 and 2pixel elements were not reproduced by the plates. With ComparativeExamples 1 and 2, the 50% dots were also removed. In ComparativeExamples 3 and 4, the 50% dots were highly attacked.

[0118] The invention has been described in detail, with particularreference to certain preferred embodiments thereof, but it should beunderstood that variations and modifications may be effected within thespirit and scope of the invention.

[0119] Having described the invention, we now claim the following andtheir equivalents.

What is claimed is:
 1. An aqueous alkaline developer comprising anaqueous solution of one or more water-soluble suppressors of thefollowing structure: R₁(CHOH)_(n)R₂ in which n is 4 to 7; and either (i)R₁ is hydrogen, aryl, or CH₂OH; and R₂ is alkyl group having 1 to 4carbon atoms, CH₂OR₃ in which R₃ is an alkyl group having 1 to 4 carbonatoms, CH₂N(R₄R₅) in which R₄ and R₅ are each independently hydrogen oran alkyl group having 1 to 4 carbon atoms, or CO₂H; or (ii) R₁ and R₂together form a carbon-carbon single bond; in which: the developer has apH of about 10.0 to about 14; and the one or more suppressors togethercomprise about 10 wt % to about 30 wt % of the developer.
 2. Thedeveloper of claim 1 in which the developer has a pH between about 12and about 13.5.
 3. The developer of claim 2 in which the developer has aconductivity of about 40 to about 80 mS/cm.
 4. The developer of claim 3in which R¹ and R² together form a carbon-carbon single bond, and n is 5or
 6. 5. The developer of claim 4 in which the suppressor ismeso-inosit.
 6. The developer of claim 3 in which R¹ is H, R² is CO₂H,and n is 4 or
 5. 7. The developer of claim 6 in which the suppressor isselected from the group consisting of ribonic acid, gluconic acid,mannonic acid, and gulonic acid.
 8. The developer of claim 3 in which R¹is hydrogen, R² is CH₂N(R⁴R⁵), and R⁴ and R⁵ are each independentlyhydrogen or an alkyl group having 1 to 2 carbon atoms.
 9. The developerof claim 8 in the suppressor is glucamine, N-methyl-glucamine, or1-desoxy-1-(methylamino)-D-galactit.
 10. The developer of claim 3 inwhich the developer does not comprise a silicate.
 11. The developer ofclaim 1 in which (i) R¹ and R² together form a carbon-carbon singlebond, and n is 5 or 6; (ii) R¹ is H, R² is CO₂H, and n is 4 or 5; or(iii) R¹ is hydrogen, R² is CH₂N(R⁴R⁵), and R⁴ and R⁵ are eachindependently hydrogen or an alkyl group having 1 to 2 carbon atoms. 12.The developer of claim 1 in which the suppressor is selected from thegroup consisting of meso-inosit, ribonic acid, gluconic acid, mannonicacid, gulonic acid, glucamine, N-methyl-glucamine, and1-desoxy-1-(methylamino)-D-galactit.
 13. The developer of claim 1 inwhich the developer additionally comprises: a total of about 0.0005 wt %to about 3 wt % of one or more polyglycol derivatives, the polyglycolderivatives selected from the group consisting of polycondensationproducts of C₂-C₄ alkylene oxides with ethylene diamine and polyglycolderivatives having the structure: R⁶O—(CH₂CHR⁷O)_(y)—R⁸ in which R⁶ ishydrogen or C₁-C₈ alkyl; R⁷ is hydrogen, methyl or ethyl; R⁸ is hydrogenor CH₂COOH; and y is about 10 to about
 20. 14. The developer of claim 1in which the developer additionally comprises at least one additiveselected from the group consisting of surfactants, biocides, antifoamingagents, and chelating agents.
 15. A method for forming an image, themethod comprising the steps of: (a) imaging an imageable element, theimageable element comprising an imageable layer over a hydrophilicsupport; and forming an imaged element comprising imaged regions andunimaged regions in the imageable layer; and (b) developing the imagedelement with an aqueous alkaline developer and removing one of theimaged regions and the unimaged regions of the imageable layer; inwhich: the aqueous alkaline developer comprises one or morewater-soluble suppressors of the following structure: R₁(CHOH)_(n)R₂ inwhich n is 4 to 7; and either (i) R₁ is hydrogen, aryl, or CH₂OH; and R₂is alkyl group having 1 to 4 carbon atoms, CH₂OR₃ in which R₃ is analkyl group having 1 to 4 carbon atoms, CH₂N(R₄R₅) in which R₄ and R₅are each independently hydrogen or an alkyl group having 1 to 4 carbonatoms, or CO₂H; or (ii) R₁ and R₂ together form a carbon-carbon singlebond; the developer has a pH of about 10.0 to about 14; and the one ormore suppressors together comprise about 10 wt % to about 30 wt % of thedeveloper.
 16. The method of claim 15 in which (i) the imageable layercomprises at least one phenolic resin or at least one polymeric compoundhaving pendent sulfonamide groups, and (ii) the hydrophilic supportcomprises aluminum or an aluminum alloy.
 17. The method of claim 16 inwhich the unimaged regions of the imaged layer are removed.
 18. Themethod of claim 16 in which the imaged regions of the imaged layer areremoved.
 19. The method of claim 16 in which the developer has a pHbetween about 12 and about 13.5.
 20. The method of claim 19 in which thedeveloper has a conductivity of 40 to 80 mS/cm.
 21. The method of claim20 in which R¹ and R² together form a carbon-carbon single bond, and nis 5 or
 6. 22. The method of claim 21 in which the suppressor ismeso-inosit.
 23. The method of claim 20 in which R¹ is H, R² is CO₂H,and n is 4 or
 5. 24. The method of claim 23 in which the suppressor isselected from the group consisting of ribonic acid, gluconic acid,mannonic acid, and gulonic acid.
 25. The method of claim 20 in which R¹is hydrogen, R² is CH₂N(R⁴R⁵), and R⁴ and R⁵ are each independentlyhydrogen or an alkyl group having 1 to 2 carbon atoms.
 26. The method ofclaim 25 in the suppressor is glucamine, N-methyl-glucamine, or1-desoxy-1-(methylamino)-D-galactit.
 27. The method of claim 20 in whichthe developer does not comprise a silicate.
 28. The method of claim 15in which (i) R¹ and R² together form a carbon-carbon single bond, and nis 5 or 6; (ii) R¹ is H, R² is CO₂H, and n is 4 or 5; or (iii) R¹ ishydrogen, R² is CH₂N(R⁴R⁵), and R⁴ and R⁵ are each independentlyhydrogen or an alkyl group having 1 to 2 carbon atoms.
 29. The method ofclaim 15 in which the suppressor is selected from the group consistingof meso-inosit, ribonic acid, gluconic acid, mannonic acid, gulonicacid, glucamine, N-methyl-glucamine, and1-desoxy-1-(methylamino)-D-galactit.
 30. The method of claim 15additionally comprising, after step (b), the step of: adding areplenisher to the developer to form a replenished developer; in which:the replenisher comprises one or more water-soluble suppressors of thefollowing structure: R₁(CHOH)_(n)R₂ in which n is 4 to 7; and either (i)R₁ is hydrogen, aryl, or CH₂OH; and R₂ is alkyl group having 1 to 4carbon atoms, CH₂OR₃ in which R₃ is an alkyl group having 1 to 4 carbonatoms, CH₂N(R₄R₅) in which R₄ and R₅ are each independently hydrogen oran alkyl group having 1 to 4 carbon atoms, or CO₂H; or (ii) R₁ and R₂together form a carbon-carbon single bond; the replenisher has a pH ofabout 11.0 to about 14; and the one or more suppressors togethercomprise about 10 wt % to about 30 wt % of the replenisher solution. 31.The method of claim 30 in which the developer has a conductivity ofabout 40 to about 80 mS/cm and the replenisher has a conductivity ofabout 60 to about 120 mS/cm.
 32. The method of claim 30 in which (i) theimageable layer comprises at least one phenolic resin or at least onepolymeric compound having pendent sulfonamide groups, and (ii) thehydrophilic support comprises aluminum or an aluminum alloy.
 33. Themethod of claim 30 in which the unimaged regions of the imaged layer areremoved.
 34. The method of claim 30 in which the imaged regions of theimaged layer are removed.
 35. The method of claim 30 in which (i) R¹ andR² together form a carbon-carbon single bond, and n is 5 or 6; (ii) R¹is H, R² is CO₂H, and n is 4 or 5; or (iii) R¹ is hydrogen, R² isCH₂N(R⁴R⁵), and R⁴ and R⁵ are each independently hydrogen or an alkylgroup having 1 to 2 carbon atoms.
 36. The method of claim 30 in whichthe suppressor is selected from the group consisting of meso-inosit,ribonic acid, gluconic acid, mannonic acid, gulonic acid, glucamine,N-methyl-glucamine, and 1-desoxy-1-(methylamino)-D-galactit.
 37. Animage formed by the method comprising the steps of: (a) imaging animageable element, the imageable element comprising an imageable layerover a hydrophilic support; and forming an imaged element comprisingimaged regions and unimaged regions in the imageable layer; and (b)forming the image by developing the imaged element with an aqueousalkaline developer and removing one of the imaged regions and theunimaged regions of the imageable layer; in which: the aqueous alkalinedeveloper comprises one or more water-soluble suppressors of thefollowing structure: R₁(CHOH)_(n)R₂ in which n is 4 to 7; and either (i)R₁ is hydrogen, aryl, or CH₂OH; and R₂ is alkyl group having 1 to 4carbon atoms, CH₂OR₃ in which R₃ is an alkyl group having 1 to 4 carbonatoms, CH₂N(R₄R₅) in which R₄ and R₅ are each independently hydrogen oran alkyl group having 1 to 4 carbon atoms, or CO₂H; or (ii) R₁ and R₂together form a carbon-carbon single bond; the developer has a pH ofabout 10.0 to about 14; and the one or more suppressors togethercomprise about 10 wt % to about 30 wt % of the developer.
 38. The imageof claim 37 in which (i) the imageable layer comprises at least onephenolic resin or at least one polymeric compound having pendentsulfonamide groups, and (ii) the hydrophilic support comprises aluminumor an aluminum alloy.